Supporting this conclusion is the observation that depletion of TGF-β signaling in γδT IELs leads to increased susceptibility to and exacerbation of DSS-induced colitis, as evidenced in both Smad3−/− mice and γδT cell-specific TGF-β receptor I-deficient mice, due to enhanced bacterial invasion and damage to the epithelial barrier resulting from the reduction of γδ IELs in these knockout mice. The gene discussed is TGFB1; the disease is colitis.